The present invention relates to cardiovascular stents which can be inserted into a body lumen. More particularly, the present invention relates to a removable cardiovascular stent designed to operate with an extraction catheter to enable easy retrieval of the implanted stent.
The implantation of a stent to maintain patency of a body lumen is well known in the art. A stent is typically a tubular metallic or polymeric body, which is carried on a dilatation catheter to a specific vascular location. In one cardiovascular application, a stent is mounted on a balloon catheter and positioned at the appropriate site within an artery. The balloon is dilated to expand the stent against the vascular wall. The balloon is thereafter deflated and removed, leaving the expanded stent in place in the artery. The stent may also be self or thermally expanding, thus, not requiring a balloon for placement. Due to the structural integrity of the stent, the arterial wall is supported by the stent and prevented from recollapsing.
One shortcoming of conventional stents is that most stents are not designed to facilitate removal following implantation. In an increasing number of instances, it has become desirable to remove a stent after implantation. Although some procedures have been developed to remove a stent from a vascular location, these methods typically. require complex instrumentation, or expose the luminal intima to undesirable levels of trauma.
For example, European Patent Application No. 0 364 420 discloses a device for transluminal implantation or extraction. The disclosed device is a removal catheter which includes an expandable jaw. The removal catheter is threaded into the body and positioned proximally of the stent. Next, the expandable jaws are pushed out of the catheter into an expanded distal position. The jaws are maneuvered along the vascular wall and are positioned to engage the exterior surface of the stent. Once the jaws engage the stent, pressure is applied to the exterior surface of the stent by contracting the jaws to force the stent to compress to a diameter small enough to fit within the removal catheter. Once the stent is compressed, the jaws are pulled back into the catheter body with the stent contained within the jaws.
One disadvantage of this extraction technique and other similar techniques is that the extraction tool, i.e., the expandable jaws, must press against the vascular wall in order to engage and compress the stent. By pressing against the vascular wall with the extraction tool, there is an increased risk of further traumatizing the treatment site. In addition, by externally compressing the stent with the jaws there is an increased risk of deforming the stent in a manner which would result in the protrusion of the stent in between the individual components of the jaws. The protruding portion of the deformed stent could potentially damage the artery upon removal of the stent.
Thus, there remains a need for an improved cardiovascular stent specially adapted for radial expansion and contraction. In addition, there remains a need for a stent manipulation device to implant and/or remove a stent with minimal trauma to the vascular wall.